Physico-Mechanical Characteristics of Earth Bricks Stabilized with Cement and Padouk Sawdust Residues

The objective of this work is to improve the physical and mechanical properties of stabilized earth blocks (BTC) used in construction in the Ndé department of Cameroon. To achieve this, two stabilizers, cement and sawdust, were used at varying percentages of 0%, 4%, 6%, and 8%. Physical characterization tests, including natural water content, specific weight, jar test, Protor, and Atterberg limits, were conducted. Additionally, mechanical tests, such as compression and three-point bending, were performed. The results show that as the amount of stabilizer increases, the density of BTC decreases. The samples with 8% sawdust have the highest density, while those without stabilizers have the lowest. Porosity decreases as sawdust and cement content increases, with smaller values observed in samples with 8% sawdust or cement. Our tests indicate that blocks stabilized with cement have slightly higher compressive strength than those stabilized with sawdust. However, the water absorption rate increases with higher sawdust content.

Assessment of Cement-Lime as Stabilizer on Mud Bricks

The aim of this study was to evaluate the compressive strength of clay bricks and their stability to water absorption by inserting stabilizers such as lime and cement of 0%, 4%, 6%, 8%, 10%, 12% to 14%. Spectrometric analysis was used to characterize the various stabilizers and the clay used, and tests of resistance and water absorption were also carried out. The clay was found to be an aluminosilicate (15.55% to 17.17% Al2O3 and 42.12% to 44.15% SiO2). The lime contains 90.84% CaO and the cement has 17.80% SiO2, 3.46% Al2O3, 2.43% Fe2O3 and 58.47% CaO in the combined form of tricalcium silicate, dicalcium silicate, tricalcium aluminate and ferro-tetra calcium aluminate. The results showed that the insertion of locally available stabilizers (lime and cement) improved the strength of the material by almost 80% when the lime was increased from 0% to 14% for 14 days. For compressed cement, a 65% increase in strength was observed under the same conditions. Strength increases with drying time, with a 52% increase in strength at 28 days compared to 14 days. Furthermore, compressed cement bricks have a more compact structure, absorbing very little water (32%). In view of all these results, cement appears to be the best stabilizer, and compression improves compressive strength and reduces water absorption.

Action of New Rare Earth Additions in Cemented Carbide

The existence form and distribution of new rare earth additions in WC-Co,WC-TiC-Co.Cemented carbide and its actions of purification,modificaiton,solid solution strengthening and restraining phase transformation have been investigated.The results have been used to elucidate property im- provement of the alloys.

Rare Earth Doped New Cemented Carbide with Ni-Co Binder for Mining

A method, doping WC with La(NO 3) 3, of producing cemented carbide with rare earth was introduced. The effects of lanthanum on the mechanical properties and microstructure of WC 9(Co 75%Ni) cemented carbide were studied and a rock drilling experiment was carried out.The experimental results show that both transverse rupture strength (TRS) and hardness of WC 9(Co 75%Ni) rare earth cemented carbides can match that of WC 9Co cemented carbide, when La 2O 3 / (Co+Ni) ratio is 0.3%, the abnormal growth of WC grain in the cemented carbide can be restrained effectively, the homogeneity of grain size in microstructure and the wear resistance are improved, which can be matchable to that of WC 9Co cemented carbide for mining.

Effects of Rare Earth Elements on Properties and Structure of WC－14TiC－8Co Cemented Carbide

The effects of rare earth (RE) elements on properties and microstructure of WC-14TiC-8Co cemented carbide have been investigated. By adding RE, the characteristics such as bending strength and impact-resistance were greatly improved. The existence form and distribution of RE in cemented carbide have also been studied by means of SEM and TEM. The results. have been used to elucidate the strengthening mechanism of RE in WC-14TiC-8Co alloy.

Rare Earth Compounds in Cemented Carbides with Trace Rare Earth Additions

The morphology,structure and distribution of the rare earth compounds in the YG8R.YT5R and YT14R cemented carbides with additions of trace light rare earths were studied with an analytical electron microscope. The particles of the rare earth compounds in these alloys are all spherical and distribute at interfaces between the Co-cement phase and WC hard phase or(TiW)C solid solution,and in the(TiW)C solid solution.In the YG8R and YTI4R alloys,the rare earth compound is RE_2O_3 with a bcc structure,while in the YT5R alloy. the rare earth compound is RE_2O_2S with a hcp structure.

Effect of Adding Rare Earth Element on Cemented Carbide YT14 by Digital Image

The properties of the cemented carbides with RE-addition were improved in our research.there is a 10% increase of the transverse rupture strength(T.R.S) of YT14RE as compared with that of YT14.The hardness and the density of YT14RE are higher than that of YT14.The cast steel was cut at a speed of 140 m/min by cutting tcols which made from YT14RE and YT14.The wear resistant of the former is 1.5 time of the latter.The samples of YT14RE and YT14 were ground and polished(the content of the RE elements is less than 0.10 wt%).This paper studied the effect of adding rare earth element on cemented carbide by digital image.

Rare earth Ce-modified (Ti,Ce)/a-C:H carbon-based film on WC cemented carbide substrate

WC cemented carbide suffers severe wear in water environments. A novel carbon-based film could be a feasible way to overcome this drawback. In this study, a rare earth Ce-modified（Ti,Ce）/a-C：H carbon-based film is successfully prepared on WC cemented carbide using a DC reactive magnetron sputtering process. The microstructure, mechanical properties,and tribological behavior of the as-prepared carbon-based film are systematically investigated. The results show that the doping Ti forms Ti C nanocrystallites that are uniformly dispersed in the amorphous carbon matrix, whereas the doping Ce forms CeO2 that exists with the amorphous phase in the co-doped（Ti,Ce）/a-C：H carbon-based film. The mechanical properties of this（Ti,Ce）/a-C：H film exhibit remarkable improvements, which could suggest higher hardness and elastic modulus as well as better adhesive strength compared to solitary Ti-doped Ti/a-C：H film. In particular, the as-prepared（Ti,Ce）/a-C：H film presents a relatively low friction coefficient and wear rate in both ambient air and deionized water,indicating that（Ti,Ce）/a-C：H film could feasibly improve the tribological performance of WC cemented carbide in a water environment.

稀有金属元素在硬质合金中的应用研究进展

综述了国内外对稀有金属元素在硬质合金中的应用研究进展,分析了四类元素稀有难熔金属、稀土、稀贵金属和稀散金属对硬质合金微观组织与性能的影响,并展望了稀有金属元素在硬质合金中的应用前景。

湿法制备Cu基Mn-Ce改性甲醇重整制氢催化剂及其催化性能研究

为了提升Cu基催化剂的高温稳定性和使用寿命,并研究过渡金属Mn及轻稀土金属Ce对Cu基甲醇重整催化剂的影响,本文采用新型湿法制备了Cu基Mn-Ce改性催化剂,并在气-固相固定床催化反应装置上评价了其甲醇重整制氢的性能。甲醇转化实验结果显示,Cu基Mn-Ce改性催化剂的甲醇转化率达到98.77%,产出的(H2+CO)含量达到92.5%。高温碳化性能对比实验结果表明,相比未改性的催化剂,Mn-Ce改性催化剂的高温稳定性更强,使用寿命更长。高温碳化后,205℃下的甲醇转化率均在40%以上,未改性催化剂的转化率仅为20%左右。催化剂性能评价实验结果表明,催化反应温度与其制氢性能呈正相关,高温下催化剂有更优异的制氢表现。Mn、Ce的加入可以有效提高Cu基催化剂甲醇重整制氢的性能。

Directional migration behavior of cerium during sintering process of mischmetal doped cemented carbide

Three observation methods were used to investigate the existing form and the behavior of rare earth during the sintering process of high activity mischmetal (RE, with lanthanum and cerium) doped WC-8%Co-0.048%RE(mass fraction) alloy with low carbon-containing level by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDXS), considering the fact that the addition amount of rare earth in the alloy is very minute. The directional migration process and mechanism of cerium were discussed. First, the sinter skin (surface) is observed. It is shown that there exists a dispersedly distributed cerium containing oxide on the sinter skin, and lanthanum in these cerium enrichment positions is very minute. Secondly, the polished section is observed, and lanthanum containing phase/micro-zone in the alloy is identified. Finally, based on the fact that the fracture of cemented carbide is resulted from the heterogeneous phase or other defects within the microstructure, the fracture surface is observed and cerium containing phase/micro-zone in the fracture source approximately 260 μm from the surface is identified. These combined observations reveal adequately the fact that lanthanum and cerium get separated and cerium predominantly migrates towards the surface during the sintering process.

Microstructures and properties of WC-20Co-1Y_2O_3 cemented carbide by hot-press and liquid phase sintering

Ultrafine tungsten carbide and fine cobalt as well as nano yttrium oxide powders were used as the raw materials. The effects of hot-press below the eutectic temperature and conventional liquid phase sintering on the structures and properties of WC-20Co-1Y2O3 cemented carbide were studied. It is shown that hot-pressed alloy has the character of isotropic properties and microstructure with homogeneous and ultrafine WC grains. However, the ultrafine and fully-densified structure is developed at the cost of the presence of large amount of cobalt-lake （unevenly distributed binder phase）, and thus lower strength. Yttrium oxide in the alloy cannot play the role of grain growth inhibitor fully when cemented carbide with high content of cobalt and ultrafine raw materials is sintered at high liquid phase sintering temperature. Peculiar platelet-enhanced bi-model structure is formed in WC-20Co-1Y2O3 cemented carbide by conventional liquid phase sintering, which points out that yttrium oxide in the alloy facilitates the formation of plate-like WC grain.

Mechanism of Improving the Wearability of WC78-TiC14-Co8 Cemented Carbide with Yttrium Addition

The influence of yttrium addition on microstructure and wearability of WC78 TiC14 Co8 cemented carbide has been studied It is shown that the wearability of the carbide tool is significantly improved by adding trace amount of yttrium and the optimal adding amount is about 0 27%(wt)(in binder) Experimental results indicate that owing to adding yttrium, in as sintered cemented carbides the sizes of carbide grains and Co rich binder regions are reduced and their size homogeneity is improved, while in the binder, both dissolved contents of tungsten and titanium and volume proportion of the ductile α Co phase with f c c lattice are increased Therefore, the strength toughness of the binder and the cemented carbide which consists of the carbides and the binder are apparently enhanced Besides, it is found that many Y 2WO 6 particles appear along the WC/WC or WC/Co rich phase interfaces in as sintered carbide alloy with yttrium addition until 4 5%(wt), showing that during liquid phase sintering process of the alloys the segregation of yttrium atoms and Y 2WO 6 forming reaction might take place on the carbide particles/liquid binder interfaces, reducing the oxide films on the surface of WC particles and strengthening the cohesion of WC particles with Co rich binder

Phase Analysis of Cemented Carbide WC-Co Boronised with Yttrium

Phase analysis for the coated surface with B 4C and Y 2O 3 of cemented carbide WC-20Co in vacuum-heating was carried out by high-temperature X-ray diffraction from ambient temperature to 1300 ℃. The results show that, the high-concentration active boron atoms are released from the boron-supply agent B 4C located on the alloy surface and diffused into the γ-phase, leading to forming the three-element boron-bearing compound W 2Co 21B 6 beside forming boron-bearing compounds on the blank surface. By contrast with boronising only, the element yttrium in boronization broadens the boronising temperature range during vacuum-sintering, catalyzes the decarbonisation decomposition of B 4C and promotes diffusion of active boron atoms into the bulk of WC-Co.

RAW MEALS CONTAINING TRACE RE OXIDES TO IMPROVE QUALITY OF CEMENT CLINKER

Clay or industrial wastes containing trace rare earth (RE) oxides as one of the components are used to burn cement clinker. When the total amount of RE oxides reaches 0. 2×10-4 - 2. 0×10-4 (wt), it has positive effect on the burnability of raw meals? and the Alite content in clinker increases. However, with the addition of lan-thanide, the formation process of clinker and the distribu-tion of lanthanide in clinker are different from those of yt-trium. If the burning temperature is 1 450 C , yttrium shiws negative effect on the formation of clinker. There-fore, to improve the quality of cement clinkern, the raw meals in which yttrium content is lower and lanthanide con-tent is higher is preferable; to reduce the consumption of coal, the raw meals that yttrium content is higher is suit-able. Using raw meals containing trace RE oxides can re-duce the cost of fluorite and protect environment.

合金添加剂对WC基硬质合金氧化行为及其关联特性的影响

为了同步改善合金的高温抗氧化性能及物理与力学性能,设计WC-6Co-6Ni、WC-6Co-6Ni-1Cr_(3)C_(2)、WC-6Co-6Ni-1CeO_(2)和WC-12Co-1CeO_(2)等4组WC基硬质合金,分别对应1^(#)~4^(#)合金,对比研究合金的微观结构、物理与力学性能和700℃连续16 h的氧化行为。结果表明,CeO_(2)弥散相的存在不会导致WC基硬质合金强度降低,合金硬度遵循复合材料硬度及晶粒度和各相体积分数的耦合作用规律。4组合金中,4^(#)合金的硬度最高,其次为2^(#)合金,Co、Ni黏结金属对硬质合金硬度的影响显著。Cr_(3)C_(2)和CeO_(2)添加剂均可显著改善700℃下合金的抗氧化性能,但Cr_(3)C_(2)的改善效果明显优于CeO_(2)。在WC基硬质合金中添加适量的Cr_(3)C_(2)和CeO_(2),并用Ni部分替代Co,可实现对合金高温抗氧化性能及物理与力学性能同步改善。

WC-8Co硬质合金中稀土添加剂的作用

以混合稀土氧化物为添加剂，在真空炉中于０２Ｐａ、１３７０℃下经液相烧结３０ｍｉｎ制备加稀土的ＷＣ８ＣｏＲ硬质合金试样。Ｘ射线衍射、扫描电镜和磁性测定的结果表明，稀土提高ＷＣ８Ｃｏ硬质合金的表面宏观压应力是强化合金的重要因素，其阻止粘结相（γ相）的ｆｃｃ→ｈｃｐ转变对合金强韧性的作用甚微。稀土对ＷＣＣｏ硬质合金显微结构参数无明显影响。

克拉玛依稠油热采井DM型系列地锚预应力固井技术

稠油热采井采用常规固井技术存在的主要问题是套管的错断、变形和泄露,而解决该问题的较好方法就是采用预应力固井技术。介绍了克拉玛依油田研制的应用于热采井预应力固井的DM型系列地锚的结构、尺寸、性能参数、工作原理、现场使用情况及应注意的问题等,举例计算了现场施工所需要施加的预应力。现场统计资料显示,预应力固井技术对防止套管损坏有明显效果。

硬质合金刀片切削过程中自润滑功能稀土氧硫化物的原位形成

考察了高活性混合稀土(RE)掺杂的WC-8%Co-0.07%RE(质量分数)硬质合金刀片对铸铁的切削试验。采用扫描电镜、能谱分析以及X射线衍射等分析方法对硬质合金烧结体表面、切削试验后刀片的前刀面、后刀面以及切削刃进行观察与分析。结果表明,在稀土硬质合金刀片切削过程中发生了La、Ce从合金内部至刀片工作表面的非同步迁移现象,在刀具工作表面原位形成了具有自润滑功能的稀土氧硫化物。在实验观察与分析基础上,对La、Ce的定向迁移机制与稀土氧硫化物的形成机制进行了探讨。

复合土壤胶结料的性能试验研究

通过大量的室内实验,分析讨论了复合土壤胶结料材料的性能,以及掺量、固化对象、养护条件等因素对材料性能的影响,并对比分析了胶结料固化土和水泥土的抗压强度及微观结构.研究结果表明:复合土壤胶结料与土壤拌合后,发生水化作用并形成具有胶凝性的水化产物使土粒固结,形成板体结构.复合土壤胶结料具有较强的适应性、较高的固结强度和良好的水稳定性.